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A.L.1                            PART I - DESCRIPTIVE
Page 15
           (d)  Power pack
                 A power pack, operated by 115 volt, 400 C/S A.C., is fitted forward
                 of the instrument panel.  This transforms and rectifies the a.c. supply
                 to give the required d.c. voltages to operate the system.
           (e)  Control of the system
                 Located on the starboard wall adjacent to the cockpit lights switches
                 is a NORMAL-RESET switch, spring loaded to the NORMAL
                 position and a neon indicator.  With the system inoperative the neon
                 indicator glows.  When the switch is held down to RESET the power
                 pack becomes active and the indicator is extinguished.  The power
                 pack remains active as long as input voltage is maintained.  This supply
                 is obtained from the flight instruments (No. 1) inverter, or from the
                 No. 2 inverter which acts as a standby (see para. 18(f)).  If the indi-
                 tor glows in flight the RESET switch must be operated to bring the
                 system back to use.

           9.   Pressure refuelling and defuelling
           (a)  Refuelling is via a connection in the port wheel bay.  As each set of
                 tanks is filled, refuelling valves automatically cut off the fuel being
                 supplied to them.  During refuelling the L.P. cock must be OFF, the
                 transfer selector cock switch at AUTO and the defuelling cock OFF.
                 A time switch adjacent to the coupling must be ON in order to ener-
                 gize the refuelling circuit.
           (b)  Defuelling is via the same coupling.  During defuelling the L.P. cock
                 must be OFF, the transfer selector cock switches at AUTO and the
                 defuelling cock ON.  An air pressure of 10 lb./sq. in. is necessary to
                 transfer fuel to the front tanks whence it is either sucked out by the
                 bowser pump or pumped out by the booster-pumps.  The air pressure
                 connection is on top of the centre fuselage.

           10.  Avon 203 engine
           (a)  General
                  The engine is a 15-stage axial-flow gas turbine developing 10,000 lb.
                  static thrust at sea level.  The main engine systems include:-
                       Variable swirl vanes.  (See para.12.)
                       A liquid fuel starting system.  (See para. 13.)
                       Relighting facilities.  (See para. 14.)
                       An anti-icing system.  (See para. 16.)
                       A high pressure fuel system controlled by a flow control unit.
                       Self contained oil system.
           (b)  High pressure fuel pumps
                  The twin engine-driven H.P. pumps share a common housing.  A
                  servo-control system controls the total pump output and a governor
                  limits overspeeding of the engine.
           (c)  Flow control unit
                  The servo control system is operated by the flow control unit.  The
                  control unit which contains the throttle valve, H.P. cock, barometric
                  pressure control (B.P.C.), acceleration control unit (A.C.U.), and
                  r.p.m. datum control varies fuel flow to the engine according to
                  throttle position, altitude, forward speed and r.p.m.
           (d)  Oil system
                  Oil is carried in the engine sump, the capacity of which is 9½ pints.
                  One pressure and four scavenge pumps maintain a continuous circu-
                  lation through a cooler and filter to the engine bearings and gears.


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